NATURE OF SPEECH AND ITS INTERPRETATION 



135 



sheet as shown in Table IV. for example it will he noticed that p 

 was recorded as k 24.4 per cent, as p 45 per cent, and as t 22.2 per cent 

 of the times called. On the other hand the sound w was only recorded 

 incorrectly 1 per cent of the times called. 



For this system the consonant articulation was 65.8 and the vowel 

 articulation 83.4. 



Description of the System for Reproducing Speech Sounds 



The telephone system used in this investigation is probably more 

 nearly perfect than any other which has yet been built. Its essential 

 elements are a condenser transmitter to receive the speech waves 

 and transform them into the electrical form, an amplifier for magni- 

 fying the intensity of the electrical speech currents, an attenuator 

 for controlling the intensity, an equalizing network, and a receiver 

 for delivering the speech to the ear. A schematic arrangement of 

 the circuit is shown in Fig. 1. 



Equalizing 

 8]/, 2 Ml. 20 V imfNetWork 



elf '^'^'' 



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'B' Battery 

 £10 l/olts 



Fig. 1. — High Quality Telephone System 



A detailed description of the construction and operation of the 

 condenser transmitter has been given by Crandall and Wente and 

 published in the Physical Review} It is simply an air condenser, 

 one of its plates being a flexible metal diaphragm. 



A five-stage vacuum tube amplifier was used. Particular care 

 was taken in coupling the stages together, so that the amplifier was 

 practically free from frequency distortion. 



The attenuator consisted of a potentiometer arrangement which 

 could reduce the amplitude of the speech waves to approximately 

 one-millionth of their maximum values. 



The equalizing network was an arrangement of resistances, con- 



» Crandall, Phys. Rev., June, 1918; Wente, Phys. Rev., July, 1917. 



